Engineered tissue implants require a tissue scaffold that is preferably made of similar materials to the tissue that will be replaced by the engineered tissue implant. This requires using biomaterials such as, but not limited to, collagen, fibrin, and glycosaminoglycans (GAGs). However, while these materials may provide the correct biomaterial environment, they lack the mechanical strength required to be implanted. Such forces may be generated from in situ forces, such as pressure from fluids passing through or by the implant. Further, the tissue implants need to be able to withstand the forces of being handled and surgically implanted by the surgeon. This is a common, long standing problem that has made designing a tissue engineering implant very difficult.
Many different techniques have been used to try to overcome the lack of mechanical strength in scaffolds, and the corresponding lack of strength in the implant. These include processing techniques such as crosslinking the materials. However, this typically does not create sufficient increased strength. In addition, the crosslinkers are usually cytotoxic, which adds the complexity of thoroughly rinsing the samples to remove excess crosslinker. Other techniques have copolymerized the biomaterials with a stiffer, usually synthesized, polymer. This greatly increases the cost of manufacturing the material and can be hard to fabricate the material into a scaffold. In addition, scaffolds have been developed from a relatively stiff synthesized polymer with pore sizes in the range of a few hundreds of microns in diameter, which have then been coated with a biomaterial. This technique can provide the strength required, but results in a mostly synthetic scaffold with minimal biomaterial that the cells cannot remodel. Once the biomaterials are degraded only the synthetic polymer remains.